The present invention relates to a trunnion support in fork eyes of universal joints. More specifically, the support consists of a cylindrical roller bearing with a bearing bushing consisting of a sleeve section and a bottom section axially supporting the trunnion and which closes the sleeve section on one side and at least two rows of cylindrical rollers arranged side by side which engage and roll between outer races in the bore of the sleeve section and inner races on the trunnion.
Supports of this general type are not new, per se. In the state of the art supports, typically the outside surface of the sleeve section of the bearing bushing is constructed so that it corresponds to the outer races of the bore of the sleeve section whereby the outside surface as well as the bore of the sleeve section are either cylindrically smooth or stepped as illustrated in German preliminary application No. 2,625,960. In the assembly illustrated in the German application, the trunnion is tapered in steps toward its end in order to form inner races for the cylindrical rollers which are arranged next to one another. This type of prior art support has several disadvantages and drawbacks. For example, it has been found that the end of the trunnion experiences high bending stresses by reason of the fact that it is of relatively small diameter and also due to the high notch stress produced at the step or juncture between the inner races of the trunnion. These combined stresses produce material fatigue and failure of the trunnion. Furthermore, a trunnion with stepped or offset inner races is rather difficult and uneconomical to manufacture.
Additionally, the bearing sleeve of this known type of support usually has a uniformly thick wall between the thick walled sleeve section of the bearing bushing and the trunnion to accommodate the cylindrical rollers. By reason of this, the cylindrical roller bearing has a relatively small bearing capacity and the only way of increasing the bearing capacity is by enlarging the width of the cylindrical roller bearing and providing additional rows of cylindrical rollers or utilizing long rollers, such as needle rollers. This alternative, however, results in an increased support width and an enlarged diameter of the universal joint which is not desirable. The width of the support cannot be arbitrarily increased since the trunnion of the cross piece of the universal joint must then be constructed with much more of a taper and thereby weakened so that the cross piece can be fitted through the fork eyes of the fork joints.
In accordance with another known prior art support, the cylindrical roller bearing consists of a row of long needle rollers wherein the inner race on the trunnion or the outer race in the bore of the sleeve is slightly tapered. This arrangement is shown in German Patent No. 1,122,781. The roller bearing, however, comprises only a single row of cylindrical rollers. The wall thickness of the sleeve and bottom section of the bearing bushing must therefore be rather thick in cross section so that axial forces produced by the trunnion on the bottom section can be transmitted without harmful buckling of the bearing bushing to the fork joint. Here again, there is a rather small radial space between the trunnion and the bearing bushing and only thin cylindrical rollers, such as needle rollers, can be installed which do not have an efficient bearing capacity in many applications and/or occupy too large an axial construction width.
With the foregoing in mind, it is an object of the present invention to provide a support for trunnions in fork eyes of universal joints by means of a cylindrical roller bearing which is characterized by novel features of construction and arrangement providing high bearing capacity and nevertheless, is of relatively compact and small construction width. The support of the present invention is also of simplified design and is rather economical to manufacture. To this end, the sleeve section of the bearing bushing has a constant diameter over the entire width of the outer surface and has outer races in its bore which are offset or stepped radially inwardly toward the bottom section and wherein the inner races are arranged side by side on the trunnion are of the same diameter without any offset or step. By this construction, the trunnion of the cross piece of the universal joint can be manufactured economically since offsets or steps do not have to be incorporated in the trunnion. Elimination of notched recesses in the trunnion produces a construction that has a high bending strength. Furthermore, by this construction, the bearing bushing adjacent its bottom section is very rigid since the bottom section can be constructed with thick walls and forms a transition at its outer edge to a relatively thick walled part of the sleeve section. Thus, high axial forces can be transmitted from the front face of the trunnion to the bottom section without resulting in a harmful buckling of the bearing bushing.
In accordance with the present invention, the sleeve section is open on the side axially opposite the bottom section and the outer races formed therein are of a relatively large diameter so that the wall thickness is extremely small in the order of only several millimeters. Correspondingly, the space between the trunnion and the sleeve section is optimally utilized in this area for accommodating large diameter cylindrical rollers with a high bearing capacity without impairing the buckling rigidity of the bearing bushing. The construction width of the cylindrical roller bearing can therefore be kept very small as a result of its high radial bearing capacity which is particularly advantageous in terms of installing the cylindrical roller bearing and in positioning the cross piece in the fork joints of the universal joint.
In accordance with another feature of the present invention, the sleeve section is supported non-elastically at its outer peripheral surface on the side of the bottom section over its entire periphery and is supported somewhat elastically at its side opposite the bottom section at least in a radial load direction of the fork eye. In this manner, there is provided a support which can accept angular deviation of the trunnion in relation to the bearing bushing without damage since the thin wall part of the sleeve section of the bearing is elastic in the radial direction and this radial load is uniformly distributed to the individual rows of cylindrical rollers in the cylindrical roller bearing when angular deviation, for example, misalignment of the axis of the trunnion occurs. Such angular deviation of the trunnion is produced in the universal joint, for example, during transmission of high moments of rotation and also as a result of mutual elastic displacement of the fork leg carrying the fork eyes of each joint.
In accordance with a further feature of the present invention, the inner races of the rows of the cylindrical rollers arranged nearest the bottom section of the bearing bushing are conical and taper slightly in a radially inwardly direction towards the bottom section. By this configuration, deleterious end pressures between the rows of cylindrical rollers arranged near the bottom section of the bearing bushing and their races do not occur when the trunnion is displaced in relation to the bearing bushing. Furthermore, these rows of cylindrical rollers run on a relatively thick walled sleeve section near the rigidifying bottom section. Thus at small loads and low moments of rotation of the universal joint, only the end of the cylindrical rollers facing away from the bottom section are bearing. Conversely with a high load, the fork legs of each fork joint are mutually displaced in the manner described above. The cylindrical rollers then bear uniformly over their entire roller length since the inner race of the cylindrical rollers of the trunnion and/or the outer race of the cylindrical rollers or of the sleeve section are slightly conically tapered corresponding to the amount of angular deviation of the trunnion.
The arrangement of the rows of cylindrical rollers installed on the side axially opposite the bottom section, that is at the open end of the bearing bushing in the sleeve section is different. At this location, the sleeve section is of a thin walled construction and is supported partly elastically in the fork eye of the fork joint at least in the direction of the radial load. Accordingly with an angular deviation of the trunnion, this load will be at least partly transmitted by the loaded cylindrical rollers to the elastic thin walled part of the sleeve section so that the cylindrical rollers obtain a relatively uniform load distributed over the roller length and to be sure with a high as well as a low moment of rotation at the universal joint. In this manner, the danger of producing end pressure is prevented for the row or rows of cylindrical rollers installed on the open side of the bearing bushing.
In accordance with another feature of the present invention, the bearing bushing may be manufactured in a deep draw and/or pressure shaping process without cutting or finishing operations and this, therefore, provides a very simple means for producing the bearing bushing which is also rather economical.